My playing mates say that my backhand is significantly my stronger side; I've been working on that slice for some time, and looked at lots of good slices (Rosewall in particular). I'm not doing a good job at that, but it's been working for me at this pace.

I don't know what your tennis goal is. If you are trying to develop modern strokes, you need to have core rotation. You are using your arm primarily for power, on both wings, which is not ideal. This guy has a good modern forehand instructional videohttp://youtu.be/EMNtq393tvo

If you are going for 1920s-esque strokes, then you are doing a good job